Polishing composition

ABSTRACT

A polishing composition comprising an improver of a ratio of a polishing rate of an insulating film to that of a stopper film, wherein the polishing rate of the stopper film is selectively decreased, comprising one or more compounds selected from the group consisting of a monoamine or diamine compound; a polyamine having three or more amino groups in its molecule; an ether group-containing amine; and a heterocyclic compound having nitrogen atom. The polishing composition can be used for removing an insulating film which has been embedded for isolation into a trench formed on a silicon substrate and sedimented outside the trench, thereby planing a surface of the silicon substrate.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an improver of a ratio of apolishing rate of an insulating film to that of a stopper film. Further,the present invention relates to a polishing composition comprising theimprover, a process for selectively increasing a ratio of a polishingrate of an insulating film to that of a stopper film using the improver,and a process for producing a substrate to be polished using theabove-mentioned polishing composition.

[0003] 2. Discussion of the Related Art

[0004] Conventionally, isolation region has been formed by a techniqueso-called LOCOS (Local Oxidation of Silicon) method. However, the LOCOSmethod does not meet the requirement for high-integration of thesemiconductor of the recent year because an effective isolation regionis narrowed in the LOCOS method. Therefore, recently, there has beenemployed a so-called STI (Shallow Trench Isolation) method comprisingdepositing a stopper film such as a silicon nitride film on a siliconsubstrate, embedding an insulating film such as a silicon oxide film ina trench part, planing an excessive insulating film in the external partof the trench by using chemical-mechanical polishing (CMP) to expose thestopper film, and thereafter removing the stopper film by etching. Inthe STI method, it is desired that a ratio of the polishing rate of theinsulating film to that of the stopper film is increased in order toprevent dishing or thinning generated during polishing of the insulatingfilm on a substrate to be polished, thereby achieving planarization ofthe insulating film.

[0005] Presently, a ceria polishing agent used as a polishing agent forSTI-CMP exhibits a high polishing rate of an insulating film, andselectively controls a polishing rate of a stopper film, therebyachieving efficient planarization. However, as compared to a silicapolishing agent, there arise some problems such that the ceria polishingagent is high in costs, and abrasive grains are not easily dispersedtherein. On the other hand, a commercially available polishing agent hasa low ratio of a polishing rate of an insulating film to that of astopper film. Therefore, there arise a problem such that polishing isundesirably progressed at parts where trench portions are closelyarranged, as compared to parts where there are fewer trench portions, sothat thinning is likely to be generated. In addition, when a stopperfilm is made thicker in order to prevent thinning, there arise a problemsuch that an insulating film in the trench part remains in a largeamount by removal of the stopper film after CMP, so that there is stillyet a great difference in the levels (step height) between a siliconsubstrate surface and an insulating film surface.

[0006] There have been reported that a ratio of polishing rates can beincreased by adding triethanolamine as disclosed in Japanese PatentLaid-Open No. Hei 11-330025, or adding tetramethylammonium hydroxide andhydrogen peroxide as disclosed in Japanese Patent Laid-Open No. Hei10-270401. However, in the former method, there arise some problems suchthat addition of a large amount of triethanolamine so as to have aconcentration of 10% by weight or more is needed in order to exhibit itseffects, thereby increasing its costs including costs for waste watertreatment. In the latter method, hydrogen peroxide is likely to bedecomposed, so that its effects, including stability, are notsufficient.

[0007] An object of the present invention is to provide an improver of aratio of a polishing rate of an insulating film to that of a stopperfilm for stably and selectively increasing the ratio of a polishing rateof an insulating film to that of a stopper film.

[0008] Another object of the present invention is to provide a polishingcomposition comprising the improver, a process for selectivelyincreasing a ratio of a polishing rate of an insulating film to that ofa stopper film, and a process for producing a substrate to be polishedusing the above-mentioned polishing composition.

[0009] These and other objects of the present invention will be apparentfrom the following description.

SUMMARY OF THE INVENTION

[0010] According to the present invention, there are provided:

[0011] [1] an improver of a ratio of a polishing rate of an insulatingfilm to that of a stopper film, wherein the polishing rate of thestopper film is selectively decreased, comprising one or more compoundsselected from the group consisting of:

[0012] (A) a monoamine compound represented by Formula (I):

[0013] wherein each of R¹, R² and R³ is independently hydrogen atom, analkyl group having 1 to 6 carbon atoms or an alkenyl group having 2 to 6carbon atoms, with proviso that a total number of carbon atoms in R¹, R²and R³ is from 1 to 8;

[0014] (B) a diamine compound represented by Formula (II):

[0015] wherein each of R⁴, R⁵, R⁷ and, R⁸ is independently hydrogenatom, an alkyl group having 1 to 6 carbon atoms or an alkanol grouphaving 1 to 6 carbon atoms; and R⁶ is a linear, branched or cyclicalkylene group having 1 to 18 carbon atoms, or a group represented byFormula (III):

[0016] wherein each of R⁹ and R¹⁰ is independently hydrogen atom or analkyl group having 1 to 6 carbon atoms; and each of a and b is aninteger of from 0 to 9, with proviso that a total number of carbon atomsin Formula (III) is from 2 to 18;

[0017] (C) a monoamine compound represented by Formula (IV):

[0018] wherein each of R¹¹, R¹² and R¹³ is independently hydrogen atom,an alkyl group having 1 to 8 carbon atoms, an alkanol group having 1 to8 carbon atoms, an alkanediol group having 1 to 8 carbon atoms, analkanetriol group having 1 to 8 carbon atoms or a group represented by—(R¹⁴O)_(c)R¹⁵; R¹⁴ is an alkylene group having 1 to 4 carbon atoms; R¹⁵is hydrogen atom, an alkyl group having 1 to 18 carbon atoms or an acylgroup having 1 to 18 carbon atoms; and c is an integer of from 1 to 20,with proviso that:

[0019] (i) at least one of R¹¹, R¹² and R¹³ is an alkanediol grouphaving 1 to 8 carbon atoms, an alkanetriol group having 1 to 8 carbonatoms or a group represented by —(R¹⁴O)_(c)R³⁵, wherein R³⁵ is an alkylgroup having 1 to 18 carbon atoms or an acyl group having 1 to 18 carbonatoms; or

[0020] (ii) in a case where at least one of R¹¹, R¹² and R¹³ is analkanol group having 1 to 8 carbon atoms or a group represented by—(R¹⁴O)_(c)H, at least one of the other groups is an alkyl group having1 to 8 carbon atoms;

[0021] (D) a polyamine having three or more amino groups in itsmolecule;

[0022] (E) an ether group-containing amine; and

[0023] (F) a heterocyclic compound having nitrogen atom;

[0024] [2] a polishing composition comprising the improver of item [1]above;

[0025] [3] a process for selectively increasing a ratio of a polishingrate of an insulating film to that of a stopper film, comprisingapplying the improver of item [1] above;

[0026] [4] a process for producing a substrate to be polished,comprising applying the polishing composition of item [2] above; and

[0027] [5] a polishing process comprising removing an insulating filmwhich has been embedded for isolation into a trench formed on a siliconsubstrate and sedimented outside the trench with the polishingcomposition of item [2] above, thereby planing a surface of the siliconsubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028]FIG. 1 is a schematic view showing a carrier surface used inExamples.

DETAILED DESCRIPTION OF THE INVENTION

[0029] In the present invention, the phrase “a ratio of a polishing rateof an insulating film to that of a stopper film, wherein the polishingrate of the stopper film is selectively decreased” is hereinafter alsoreferred to as ‘selective ratio.’ Therefore, the term “improver of aratio of a polishing rate of an insulating film to that of a stopperfilm” (hereinafter also referred to as “improver of a selective ratio”)refers to an agent having an action of increasing a ratio of a polishingrate of an insulating film to that of a stopper film in STI method bycontaining the improver of a selective ratio in the polishingcomposition, concretely, having an action of reducing the polishing rateof a stopper film without remarkably lowering the polishing rate of theinsulating film. Here, as to the ratio of polishing rates to beincreased by the improver of a selective ratio, i.e. (polishing rate ofinsulating film)/(polishing rate of stopper film), the improver of aselective ratio preferably has a selective ratio exceeding 3 to 4 thatof the commercially available silica polishing agent, from the viewpointof facilitating the detection of the end point of polishing (viewpointof being capable of easily stopping polishing at a given position), andthe viewpoint of planing a substrate to be polished after polishing. Theselective ratio is preferably 6 or more, more preferably 8 or more,still more preferably 10 or more, especially preferably 15 or more. Thepolishing rate of each film is that determined by the method describedin Examples set forth below.

[0030] The improver of a selective ratio of the present inventioncomprises, as described above, one or more compounds selected from thegroup consisting of:

[0031] (A) a monoamine compound represented by Formula (I):

[0032] wherein each of R¹, R² and R³ is independently hydrogen atom, analkyl group having 1 to 6 carbon atoms or an alkenyl group having 2 to 6carbon atoms, with proviso that a total number of carbon atoms in R¹, R²and R³ is from 1 to 8;

[0033] (B) a diamine compound represented by Formula (II):

[0034] wherein each of R⁴, R⁵, R⁷ and R⁸ is independently hydrogen atom,an alkyl group having 1 to 6 carbon atoms or an alkanol group having 1to 6 carbon atoms; and R⁶ is a linear, branched or cyclic alkylene grouphaving 1 to 18 carbon atoms, or a group represented by Formula (III):

[0035] wherein each of R⁹ and R¹⁰ is independently hydrogen atom or analkyl group having 1 to 6 carbon atoms; and each of a and b is aninteger of from 0 to 9, with proviso that a total number of carbon atomsin Formula (III) is from 2 to 18;

[0036] (C) a monoamine compound represented by Formula (IV):

[0037] wherein each of R¹¹, R¹² and R¹³ is independently hydrogen atom,an alkyl group having 1 to 8 carbon atoms, an alkanol group having 1 to8 carbon atoms, an alkanediol group having 1 to 8 carbon atoms, analkanetriol group having 1 to 8 carbon atoms or a group represented by—(R¹⁴O)_(c)R¹⁵; R¹⁴ is an alkylene group having 1 to 4 carbon atoms; R¹⁵is hydrogen atom, an alkyl group having 1 to 18 carbon atoms or an acylgroup having 1 to 18 carbon atoms; and c is an integer of from 1 to 20,with proviso that:

[0038] (i) at least one of R¹¹, R¹² and R¹³ is an alkanediol grouphaving 1 to 8 carbon atoms, an alkanetriol group having 1 to 8 carbonatoms or a group represented by —(R¹⁴O)_(c)R³⁵, wherein R³⁵ is an alkylgroup having 1 to 18 carbon atoms or an acyl group having 1 to 18 carbonatoms; or

[0039] (ii) in a case where at least one of R¹¹, R¹² and R¹³ is analkanol group having 1 to 8 carbon atoms or a group represented by—(R¹⁴O)_(c)H, at least one of the other groups is an alkyl group having1 to 8 carbon atoms;

[0040] (D) a polyamine having three or more amino groups in itsmolecule;

[0041] (E) an ether group-containing amine; and

[0042] (F) a heterocyclic compound having nitrogen atom.

[0043] In Formula (I), each of R¹, R² and R³ is hydrogen atom, an alkylgroup having 1 to 6 carbon atoms, or an alkenyl group having 2 to 6carbon atoms. Each of R¹, R² and R³ is an alkyl group having preferably1 to 4 carbon atoms, more preferably 1 to 3 carbon atoms, from theviewpoint of increase in the selective ratio. In addition, the totalnumber of carbon atoms in R¹, R² and R³ is preferably from 1 to 6, morepreferably from 1 to 4, still more preferably from 1 to 3, from theviewpoint of the increase in the selective ratio. In addition, primaryamines and secondary amines are preferable, and the primary amines aremore preferable, from the viewpoint of the increase in the selectiveratio. Further, the alkyl groups may have a linear structure, a branchedstructure or a cyclic structure, and a linear structure or a branchedstructure is preferable.

[0044] Concrete examples of the monoamine compound represented byFormula (1) include methylamine, ethylamine, propylamine,isopropylamine, butylamine, isobutylamine, sec-butylamine, pentylamine,hexylamine, dimethylamine, diethylamine, dipropylamine,diisopropylamine, methylethylamine, trimethylamine, triethylamine,allylamine, diallylamine, N,N-dimethylallylamine, N-methyldiallylamine,cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine,and the like. Methylamine, ethylamine, propylamine, isopropylamine,dimethylamine, diethylamine, dipropylamine and diisopropylamine arepreferable, from the viewpoint of the increase in the selective ratio.Particularly preferable are propylamine and isopropylamine. These aminecompounds may be used alone or in admixture of two or more kinds.

[0045] In Formula (II), each of R⁴, R⁵, R⁷ and R⁸ is hydrogen atom, analkyl group having 1 to 6 carbon atoms or an alkanol group having 1 to 6carbon atoms. Each of R⁴, R⁵, R⁷ and R⁸ is preferably hydrogen atom, analkyl group having 1 to 4 carbon atoms or an alkanol group having 1 to 4carbon atoms, more preferably hydrogen atom, an alkyl group having 1 to3 carbon atoms or an alkanol group having 1 to 3 carbon atoms, whereinthe alkyl group or the alkanol group may have a linear structure or abranched structure, from the viewpoint of the solubility in water andthe viewpoint of the increase in the selective ratio, in addition, R⁶ isa linear, branched or cyclic alkylene group having 1 to 18 carbon atoms,or a group represented by Formula (III). Among them, the grouprepresented by Formula (III) is preferable, from the viewpoint of theincrease in the selective ratio.

[0046] Each of R⁹ and R¹⁰ is hydrogen atom or an alkyl group having 1 to6 carbon atoms. Each of R⁹ and R¹⁰ is preferably hydrogen atom or analkyl group having 1 to 4 carbon atoms, more preferably hydrogen atom oran alkyl group having 1 to 3 carbon atoms, from the viewpoint of thesolubility in water and the viewpoint of the increase in the selectiveratio,. In addition, each of a and b is an integer of from 0 to 9. Eachof a and b is an integer of preferably from 0 to 8, more preferably from0 to 5, especially preferably from 0 to 3, from the viewpoint of thesolubility in water and the viewpoint of the increase in the selectiveratio. In addition, a +b is preferably from 1 to 11, more preferablyfrom 1 to 9, still more preferably from 1 to 7, especially preferablyfrom 1 to 5. Further, the total number of carbon atoms in Formula (III)is from 2 to 18, preferably from 2 to 16, more preferably from 2 to 12,especially preferably from 2 to 10, from the viewpoint of the increasein the selective ratio.

[0047] Concrete examples of the diamine compound represented by Formula(II) include ethylenediamine, 1,2-diaminopropane, 1,3-propanediamine,1,4-butanediamine, N,N-dimethylethylenediamine,N,N′-dimethylethylenediamine, N-ethylethylenediamine,N-methyl-1,3-propanediamine, pentamethylenediamine, 1,3-diaminopentane,N-isopropylethylenediamine, hexamethylenediamine,N-isopropyl-1,3-propanediamine, N,N,N′,N′-tetramethylethylenediamine,heptamethylenediamine, N,N,N′,N′-tetramethyl-1,2-propanediamine,N,N,N′,N′-tetramethyl-1,3-propanediamine,N,N,2,2-tetramethyl-1,3-propanediamine, octamethylenediamine,N,N′-dimethyl-1,6-diaminohexane,N,N,N′,N′-tetramethyl-1,4-butanediamine, nonamethylenediamine,N,N,N′,N′-tetramethyl-2,2-dimethyl-1,3-propanediamine,decamethylenediamine, N,N,N′,N′-tetramethyl-1,6-diaminohexane,undecamethylenediamine, 3-(dibutylamino)propylamine,dodecamethylenediamine, cyclohexanediamine,2-hydroxyethylaminopropylamine, diethanolaminopropylamine, and the like.

[0048] Among them, ethylenediamine, 1,2-diaminopropane,1,3-propanediamine, 1,4-butanediamine, hexamethylenediamine andN,N,N′,N′-tetramethyl-1,6-diaminohexane are preferable, from theviewpoint of the solubility in water and the viewpoint of the increasein the selective ratio. N,N,N′,N′-tetramethyl-1,6-diaminohexane areespecially preferable. These amine compounds may be used alone or inadmixture of two or more kinds.

[0049] In Formula (IV), each of R¹¹, R¹² and R¹³ is hydrogen atom, analkyl group having 1 to 8 carbon atoms, an alkanol group having 1 to 8carbon atoms, an alkanediol group having 1 to 8 carbon atoms, analkanetriol group having 1 to 8 carbon atoms or a group represented by˜(R¹⁴O)_(c)R¹⁵. Here, R¹⁴ is an alkylene group having 1 to 4 carbonatoms. R¹⁴ is an alkylene group having preferably 2 or 3 carbon atoms,from the viewpoint of the solubility in water. R¹⁵ is hydrogen atom, analkyl group having 1 to 18 carbon atoms or an acyl group having 1 to 18carbon atoms. R¹⁵ is preferably hydrogen atom or an alkyl group having 1to 12 carbon atoms, more preferably hydrogen atom or an alkyl grouphaving 1 to 6 carbon atoms, still more preferably hydrogen atom or analkyl group having 1 to 4 carbon atoms, from the viewpoints of theincrease in the selective ratio and the stability. In addition, c is aninteger of from 1 to 20. c is an integer of preferably from 1 to 10,more preferably from 1 to 8, especially preferably from 1 to 5, from theviewpoint of the increase in the selective ratio. In addition, as to thenumber of carbon atoms in the alkyl group, the alkanol group, thealkanediol group or the alkanetriol group for R¹¹ to R¹³, the number ofcarbon atoms in the alkyl group is preferably from 1 to 6, morepreferably from 1 to 4, especially preferably from 1 to 3, from theviewpoint of the increase in the selective ratio. The alkyl chain mayhave a linear structure or a branched structure. In addition, the numberof carbon atoms in each of the alkanol group, the alkanediol group orthe alkanetriol group is preferably from 2 to 8, more preferably from 3to 6. Here, at least one of R¹¹, R¹² and R¹³ is an alkanediol grouphaving 1 to 8 carbon atoms, an alkanetriol group having 1 to 8 carbonatoms or a group represented by ˜(R¹⁴O)_(c)R³⁵, wherein R³⁵ is an alkylgroup having 1 to 18 carbon atoms or an acyl group having 1 to 18 carbonatoms. Alternatively, in a case where at least one of R¹¹, R¹² and R¹³is an alkanol group having 1 to 8 carbon atoms or a group represented by—(R¹⁴O)_(c)H, at least one of the other groups is an alkyl group having1 to 8 carbon atoms. In the case where two of R¹¹, R¹² and R¹³ are agroup represented by —(R¹⁴O)_(c)R¹⁵, each of R¹⁴, R¹⁵ and c in eachgroup may be identical or different.

[0050] Concrete examples of the monoamine compound represented byFormula (IV) include 2-(methylamino)ethanol, N-ethyldiethanolamine,3-(methylamino)propanol, N-methyldipropanolamine, 2-(ethylamino)ethanol,2-(dimethylamino)ethanol, 4-(methylamino)dibutanol,2-(isopropylamino)ethanol, 1-(dimethylamino)-2-propanol,4-(dimethylamino)-1-butanol, 4-(ethylamino)-1-butanol,3-(diethylamino)-1-propanol, 1-(diethylamino)-2-propanol,6-(dimethylamino)-1-hexanol, 2-(diisopropylamino)ethanol,2-(dibutylamino)ethanol, N,N-dimethylethoxyethanolamine,N,N-dimethylethoxyethoxyethanolamine, N,N-diethylethoxyethanolamine,N,N-diethylethoxyethoxyethanolamine, 2-amino-1,3-propanediol,3-amino-1,2-propanediol, 2-amino-2-methyl-1,3-propanediol,2-amino-2-ethyl-1,3-propanediol, 3-diethylamino-1,2-propanediol,3-dimethylamino-1,2-propanediol, 3-methylamino-1,2-propanediol,tris(hydroxymethyl)aminomethane, ethoxypropylamine,3-methoxypropylamine, 2-methoxyethylamine, 3-propoxypropylamine,3-isobutoxypropylamine, bis(2-methoxyethyl)amine, and the like. Amongthem, 6-(dimethylamino)-1-hexanol is especially preferable, from theviewpoint of the increase in the selective ratio. These amine compoundsmay be used alone or in admixture of two or more kinds.

[0051] The polyamine having three or more amino groups in its moleculeincludes a compound represented by Formula (V):

[0052] wherein each of R¹⁶, R¹⁷, R²¹, R²³ and R²⁴ is independentlyhydrogen atom or an alkyl group having 1 to 6 carbon atoms; each of R¹⁸,R²⁰ and R²² is independently an alkylene group having 1 to 18 carbonatoms; and R¹⁹ is hydrogen atom, an alkyl group having 1 to 6 carbonatoms or a group represented by Formula (VI):

[0053] wherein R²⁵ is an alkylene group having 1 to 18 carbon atoms; andeach of R²⁶ and R²⁷ is independently hydrogen atom or an alkyl grouphaving 1 to 6 carbon atoms; and

[0054] d is an integer of from 0 to 20, and

[0055] an amino group-containing polymer compound.

[0056] Here, each of R¹⁶, R¹⁷, R²¹, R²³, R²⁴, R²⁶ and R²⁷ is hydrogenatom or an alkyl group having 1 to 6 carbon atoms. Each of R¹⁶, R¹⁷,R²¹, R²³, R²⁴, R²⁶ and R²⁷ is preferably hydrogen atom or an alkyl grouphaving 1 to 3 carbon atoms, from the viewpoint of the increase in theselective ratio. In addition, each of R¹⁸, R²⁰, R²² and R²⁵ is analkylene group having 1 to 18 carbon atoms. Each of R¹⁸, R²⁰, R²² andR²⁵ is an alkylene group having preferably 2 to 12 carbon atoms, morepreferably 2 to 6 carbon atoms, from the viewpoint of the increase inthe selective ratio. In addition, d is an integer of from 0 to 20. d ispreferably from 0 to 6, more preferably from 0 to 4, still morepreferably from 0 to 1, from the viewpoint of the increase in theselective ratio. Incidentally, in a case where d is 2 or more, pluralR²⁰ and plural R²¹ groups may respectively be identical to or differentfrom each other.

[0057] Concrete examples of the polyamine having three or more aminogroups in its molecule include diethylenetriamine,bis(3-aminopropyl)amine, N-methyl-3,3′-iminobis(propylamine),bis(hexamethylene)triamine, spermidine, spermine, triethylenetetramine,N,N′-bis(2-aminopropyl)ethylenediamine,N,N′-bis(2-aminoethyl)-1,3-propanediamine,N,N′-bis(3-aminopropyl)-1,3-propanediamine, tris(2-aminoethyl)amine,N,N,N′,N′,N″-pentamethyldiethylenetriamine, tetraethylenepentamine,polyethyleneimine, polyvinylamine, and the like. Among them,bis(3-aminopropyl)amine and triethylenetetramine are preferable, fromthe viewpoint of the increase in the selective ratio. These polyamineshaving three or more amino groups in their molecules may be used aloneor in admixture of two or more kinds.

[0058] The ether group-containing amine includes a compound representedby

[0059] wherein each of R²⁸, R²⁹, R³³ and R³⁴ is independently hydrogenatom or an alkyl group having 1 to 6 carbon atoms; each of R³⁰ and R³²is independently an alkylene group having 1 to 18 carbon atoms; R³¹ isan alkylene group having 1 to 4 carbon atoms; and e is an integer offrom 0 to 20.

[0060] Here, each of R²⁸, R²⁹, R³³ and R³⁴ is hydrogen atom or an alkylgroup having 1 to 6 carbon atoms. Each of R²⁸, R²⁹, R³³ and R³⁴ ispreferably hydrogen atom or an alkyl group having 1 to 3 carbon atoms,from the viewpoint of the increase in the selective ratio. Each of R³⁰and R³² is an alkylene group having 1 to 18 carbon atoms. Each of R³⁰and R³² is an alkylene group having preferably 2 to 12 carbon atoms,more preferably 2 to 6 carbon atoms, from the viewpoint of the increasein the selective ratio. In addition, e is an integer of from 0 to 20. eis preferably from 0 to 10, more preferably from 0 to 8, still morepreferably from 0 to 5, from the viewpoint of the increase in theselective ratio. In the case where e is 2 or more, plural R³⁰ may beidentical to or different with each other.

[0061] Concrete examples of the ether group-containing amine includebis(3-aminopropyl) ether, dimethylaminoethoxypropylamine,1,2-bis(2-aminoethoxy)ethane, 1,2-bis(3-aminopropoxy)ethane,4,9-dioxa-1,12-dodecanediamine, diethylene glycol bis(3-aminopropyl)ether, and the like. Among them, diethylene glycol bis(3-aminopropyl)ether is preferable, from the viewpoint of the increase in the selectiveratio. These ether group-containing amines may be used alone or inadmixture of two or more kinds.

[0062] Various compounds may be used as the heterocyclic compound havingnitrogen atom, and heterocyclic compounds in which one or more nitrogenatoms constituting the heterocyclic ring are secondary amines arepreferable, from the viewpoint of the increase in the selective ratio.

[0063] Concrete examples of the heterocyclic compound having nitrogenatom include piperidine, piperazine, homopiperazine, pyrrolidine,pyridine, pyrazine, pyrrole, triethylenediamine, morpholine,2-aminopyridine, 3-aminopyridine, 4-aminopyridine,3-amino-1,2,4-triazole, N-(3-aminopropyl)morpholine,N-(2-aminoethyl)morpholine, N-aminoethylpiperidine,N-aminopropylpiperidine, 1-amino-4-methylpiperazine, 2-methylimidazole,4-methylimidazole, 1,3-di(4-piperidyl)propane, 2,6-dimethylpiperazine,2,5-dimethylpiperazine, 3,5-dimethylpyrazole,bis(3-aminopropyl)piperazine, aminoethylpiperazine,hydroxyethylpiperazine, pipecoline, 2-(1-piperazinyl)pyrimidine,4-piperidinopyridine, pyridinemethanol, N-methylpiperazine,2-methylpiperazine, N-methylpiperidine, 3-piperidinemethanol,4-hydroxypiperidine, and the like. Among them, piperazine and piperidineare preferable, from the viewpoint of the increase in the selectiveratio. These heterocyclic compounds having nitrogen atom may be usedalone or in admixture of two or more kinds.

[0064] Further, the monoamine compound represented by Formula (I), thediamine compound represented by Formula (II), the monoamine compoundrepresented by Formula (IV), the polyamine having three or more aminogroups in its molecule, the ether group-containing amine and theheterocyclic compounds having nitrogen atom may be used in admixture oftwo or more kinds.

[0065] In the present invention, by using the above-mentioned improverof a selective ratio in a polishing composition, there is exhibited anexcellent effect that the selective ratio of a polishing rate of aninsulating film to that of a stopper film can be increased stably and ina low cost in the polishing according to the STI method. The reason whythe above-mentioned effect is exhibited is presumably due to the factthat the above-mentioned improver of a selective ratio is selectivelyadsorbed on the stopper film surface, thereby controlling the polishingrate of the stopper film.

[0066] Accordingly, the present invention provides a process forselectively increasing a selective ratio of a polishing rate of aninsulating film to that of a stopper film using the above-mentionedimprover of a selective ratio.

[0067] The polishing composition of the present invention comprises theabove-mentioned improver of a selective ratio. The amount of theimprover of a selective ratio is preferably from 0.01 to 20% by weight,more preferably from 0.1 to 15% by weight, still more preferably from0.3 to 10% by weight, most preferably from 0.5 to 5% by weight, of theentire amount of the polishing composition, from the viewpoint ofselectively controlling the polishing rate of the stopper film withoutdrastically reducing the polishing rate of the insulating film and theviewpoint of the surface properties of the substrate after polishing.

[0068] It is preferable that the polishing composition of the presentinvention further comprises a pH adjusting agent and/or an abrasive.

[0069] The pH of the polishing composition is preferably from 8 to 13,more preferably from 10 to 13, from the viewpoint of showing a highpolishing rate of the insulating film. A pH adjusting agent is used inorder to adjust the pH in such a manner.

[0070] As the pH adjusting agent, an alkaline source such as ammonia(concretely an aqueous ammonia), potassium hydroxide or an amine can beappropriately used. Incidentally, since the above-mentioned improver ofa selective ratio has a pH adjusting ability, when this improver of aselective ratio is used, the use of the above-mentioned alkali sourcecan be omitted, or the amount of the alkali source used can be reduced.In addition, the content of the pH adjusting agent is preferably from0.001 to 5% by weight, more preferably from 0.01 to 3% by weight, stillmore preferably from 0.1 to 1% by weight, of the entire amount of thepolishing composition, from the viewpoint of the increase in theselective ratio.

[0071] As the abrasive used in the present invention, any abrasivesgenerally employed for polishing can be used. Examples of the abrasiveinclude metals: carbides of metals or metalloids, nitrides of metals ormetalloids, oxides of metals or metalloids, borides of metals ormetalloids; diamond, and the like. The metals or metalloids includethose elements belonging to the Groups 2A, 2B, 3A, 3B, 4A, 4B, 5A, 6A,7A or 8 of the Periodic Table (long period form). Concrete examples ofthe abrasive include a-alumina particles, silicon carbide particles,diamond particles, magnesium oxide particles, zinc oxide particles,cerium oxide particles, zirconium oxide particles, colloidal silicaparticles, fumed silica particles, and the like. Among them, silica ispreferable, from the viewpoints of giving excellent dispersibility ofthe abrasive and surface properties of the substrate after polishing.More preferable are the colloidal silica prepared by a process using analkali silicate or an alkoxysilane as a starting raw material; and fumedsilica prepared by high-temperature hydrolysis of a volatile siliconcompound such as silicon tetrachloride in oxyhydrogen flame. The averageparticle size of the abrasive, as calculated from the specific surfacearea determined by the BET method, is preferably from 1 to 1000 nm, morepreferably from 5 to 500 nm, still more preferably from 10 to 300 nm,from the viewpoint of increasing the polishing rate. The amount of theabrasive is preferably from 0.5 to 30% by weight, more preferably from 1to 25% by weight, still more preferably from 3 to 15% by weight, of theentire amount of the polishing composition, from the viewpoint ofincreasing the polishing rate.

[0072] The polishing composition of the present invention, whichcomprises the improver of a selective ratio, or the improver of aselective ratio and a pH adjusting agent, is effective for a polishingprocess using a fixed grinding wheel, a polishing pad in which theabrasive grains are fixed in the pad, and the like. Further, thepolishing composition comprising the above-mentioned abrasive iseffective for a polishing process employing loose abrasives using apolishing pad made of polyurethane, and the polishing composition isalso effective for a polishing process using a fixed grinding wheel, apolishing pad in which the abrasive grains are fixed in the pad, and thelike.

[0073] The balance of the polishing composition of the present inventionis water. The water content is preferably from 45 to 99.49% by weight,more preferably from 55 to 99% by weight, still more preferably from 65to 95% by weight, of the entire amount of the polishing composition,from the viewpoint of the increase in the selective ratio.

[0074] In addition, the polishing composition of the present inventioncan optionally comprise other component including a disinfectant and anantibacterial agent, such as tetramethylammonium chloride,tetraethylammonium chloride, tetramethylammonium hydroxide,tetraethylammonium hydroxide, benzalkonium chloride, and benzethoniumchloride.

[0075] The concentration of each of the components in theabove-mentioned polishing composition is a preferable concentrationduring polishing, and the concentration may be that at the time thecomposition is prepared. The polishing composition may be prepared as aconcentrate, and used by dilution upon use.

[0076] By using the polishing composition of the present inventionhaving the above-mentioned constitution, there is exhibited an excellenteffect that a substrate to be polished having an extremely smalldifference between the level of a silicon substrate surface afterremoving the stopper film and the level of the insulating film surfaceon the trench part can be obtained stably and at a low cost, in thepolishing according to the STI method.

[0077] The polishing composition of the present invention is suitablyused in, for instance, the STI method comprising removing an insulatingfilm which has been embedded for isolation into a trench formed on asilicon substrate and sedimented outside the trench, thereby planing asurface of the silicon substrate.

[0078] In addition, the process for producing a substrate to be polishedof the present invention is carried out by using the polishingcomposition of the present invention. Here, by polishing with thepolishing composition comprising the improver of a selective ratio ofthe present invention, the selective ratio of a polishing rate of aninsulating film to that of a stopper film is increased, so that anexcellent planarization can be carried out. In addition, the thicknessof the stopper film such as a silicon nitride film can be reducedwithout causing a defect such as thinning in a substrate to be polisheddue to the planarization, so that high integration of semiconductors canbe attained.

[0079] The substrate to be polished used in the present invention is asubstrate which is obtained by an isolation step comprising embedding aninsulating film in a trench formed on a silicon substrate, such as theSTI method. The substrate to be polished comprises an insulating film,which is an object to be polished, and a stopper film for controllingthe progress of polishing.

[0080] The insulating film used in the present invention is preferably asilicon oxide film, among which a plasma TEOS film, an atmospheric CVDfilm, a thermal oxidation film and the like can be used. On the otherhand, the stopper film is preferably a silicon nitride film, among whicha low pressure CVD film, an atmospheric CVD film and the like can beused. The properties, such as thickness, of the insulating film and thestopper film are not particularly limited.

[0081] In the process for producing a substrate to be polished of thepresent invention, in order to remove an excess insulating film formedon the silicon substrate during an isolation step comprising embeddingan insulating film in a trench formed on a silicon substrate, such asthe STI method, a planed, substrate to be polished can be efficientlyprepared by polishing with the polishing composition comprising theimprover of a selective ratio.

EXAMPLES

[0082] The expression “% by weight” in Examples is made on the basis ofthe entire weight of the polishing composition. As the polishing device,a single-sided polishing machine (product number: MA-300, manufacturedby Engis Corporation) was used. The polishing conditions are givenbelow.

[0083] 1) Polishing Conditions

[0084] In Examples, as a substrate to be polished, there were used asilicon substrate (4 cm in length×4 cm in width) obtained by vapordeposition of a silicon oxide film (oxide film serving as an insulatingfilm) on the substrate surface in a thickness of 10000Å (1000 nm) bymeans of plasma TEOS, and a silicon substrate (4 cm in length ×4 cm inwidth) obtained by vapor deposition of a silicon nitride film (nitridefilm serving as a stopper film) on the substrate surface in a thicknessof 3000Å (300 nm) by means of low pressure CVD.

[0085] As the polishing pad, there was used IC 1400(P) having an outerdiameter of 30 cmΦ, manufactured by Rodel Nitta K. K. Also, thepolishing pressure was 2.5×10⁴ Pa, the flow rate of the polishing agentwas 50 mL/min. The disc rotational speed was 80 rpm, and the number ofrotations for polishing head was 60 rpm, wherein the disc and the headwere rotated in the same rotation. The polishing time was 3 minutes.Further, a water-sticking backing film was pasted on a supportingplatform made of a ceramic used for a polishing head, and a carrier 1made of a glass epoxy resin was pasted thereon. A substrate to bepolished 2 was adhered to the carrier 1 (see FIG. 1).

[0086] 2) Calculation of Polishing Rate

[0087] The polishing rate was determined by carrying out polishing underthe conditions mentioned above, determining an average value of thechange in the polishing film thickness of each substrate to be polishedbefore and after polishing, and dividing the resulting average value bythe polishing time. The amount of change in the film thickness wascalculated by obtaining a film thickness from an ellipsometer(MARY-102LD, manufactured by Five Lab K. K.).

[0088] 3) Calculation of Selective Ratio of Polishing Rate

[0089] The selective ratio of a polishing rate was calculated bydividing the polishing rate of the oxide film by the polishing rate ofthe nitride film.

EXAMPLES 1 to 11 AND COMPARATIVE EXAMPLES 1 to 5

[0090] A commercially available silica polishing agent (trade name “SemiSperse 25,” manufactured by Cabot Corporation, containing potassiumhydroxide as a pH adjusting agent) was well shaken before use. Afterhaving confirmed that there was no sedimentation of the abrasive, 15 gof propylamine was added to 260 g of the polishing agent, andion-exchanged water was added to the mixture to make up a total volumeof 500 g (propylamine concentration: 3% by weight), to give a polishingcomposition of Example 1. After stirring the polishing composition, eachof the oxide film and the nitride film was polished under theabove-mentioned polishing conditions The polishing compositions ofExamples 3 to 11 and Comparative Examples 1 to 5 were obtained by thesame procedures as in Example 1, except for using the improver of aselection ratio and the pH adjusting agent shown in Table 1. Then, thesame polishing procedures as in Example 1 were carried out for Examples3 to 11 and Comparative Examples 1 to 5. As to Example 2, a commerciallyavailable silica polishing agent ILD1300 (trade name, manufactured byRodel Nitta K. K.) was well shaken before use; having confining thatthere was no sedimentation of silica therein, 5 g (concentration: 1% byweight) of ethylenediamine was added to 495 g of the polishing agent, togive a polishing composition. After stirring, each of the oxide film andthe nitride film was polished under the above-mentioned polishingconditions. The results are shown in Table 1. TABLE 1 Polishing RateSelective Improver of Selective Ratio Classification (nm/minute) Ratioof Content of Improver of Oxide Nitride Polishing pH Adjusting No. Kind(% by wt) Selective Ratio Film Film Rates Agent pH Ex. 1 Propylamine 3.0Formula (I) 204 13 16.0 Potassium Hydroxide 12.0 Ex. 2 Ethylenediamine1.0 Formula (II) 420 60 7.0 Ammonia 12.0 Ex. 3 Isopropylamine 3.0Formula (I) 206 12 17.2 Potassium Hydroxide 12.0 Ex. 4 Diethylamine 3.0Formula (I) 160 30 5.3 Potassium Hydroxide 12.0 Ex. 5 Dipropylamine 3.0Formula (I) 208 30 6.9 Potassium Hydroxide 12.0 Ex. 6 KL-1¹⁾ 1.0 Formula(II) 120 2 60.0 Potassium Hydroxide 12.0 Ex. 7 KL-25²⁾ 5.0 Formula (IV)196 8 24.5 Potassium Hydroxide 12.0 Ex. 8 Bis(3-aminopropyl)- 2.0Formula (V) 154 18 8.4 Potassium Hydroxide 12.0 amine Ex. 9Triethylenetetramine 2.0 Formula (V) 163 13 13.0 Potassium Hydroxide12.0 Ex. 10 Diethylene glycol 3.0 Formula (VII) 178 6 32.0 PotassiumHydroxide 12.0 bis(3-aminopropyl) Ether Ex. 11 Piperazine 5.0Heterocyclic 199 7 29.6 Potassium Hydroxide 12.0 Compound Comp. — — —200 50 4.0 Potassium Hydroxide 11.0 Ex. 1 Comp. Triethanolamine 1.0 —140 46 3.0 Potassium Hydroxide 12.0 Ex. 2 Comp. Triethanolamine 3.0 —124 45 2.8 Potassium Hydroxide 12.0 Ex. 3 Comp. Triethanolamine 5.0 —110 46 2.4 Potassium Hydroxide 12.0 Ex. 4 Comp. TMAH³⁾ 3.0 — 40 10 4.0Potassium Hydroxide 12.0 Ex. 5

[0091] It can be seen from the results shown in Table 1 that thepolishing compositions of Examples 1 to 11 each comprising the improverof a selective ratio of the present invention have markedly increasedselective ratios of polishing rates, as compared to the polishingcompositions of Comparative Examples 1 to 5.

[0092] By using the polishing composition comprising the improver of aselective ratio of a polishing rate of an insulating film to that of astopper film of the present invention, the ratio of a polishing rate ofan insulating film to that of a stopper film can be increased.

[0093] The present invention being thus described, it will be obviousthat the same may be varied in many ways. Such variations are not to beregarded as a departure from the spirit and scope of the invention, andall such modifications as would be obvious to one skilled in the art areintended to be included within t the scope of the following claims.

What is claimed is:
 1. An improver of a ratio of a polishing rate of aninsulating film to that of a stopper film, wherein the polishing rate ofthe stopper film is selectively decreased, comprising one or morecompounds selected from the group consisting of: (A) a monoaminecompound represented by Formula (I):

 wherein each of R¹, R² and R³ is independently hydrogen atom, an alkylgroup having 1 to 6 carbon atoms or an alkenyl group having 2 to 6carbon atoms, with proviso that a total number of carbon atoms in R¹, R²and R³ is from 1 to 8; (B) a diamine compound represented by Formula(II):

 wherein each of R⁴, R⁵, R⁷ and R⁸ is independently hydrogen atom, analkyl group having 1 to 6 carbon atoms or an alkanol group having 1 to 6carbon atoms; and R⁶ is a linear, branched or cyclic alkylene grouphaving 1 to 18 carbon atoms, or a group represented by Formula (III):

 wherein each of R⁹ and R¹⁰ is independently hydrogen atom or an alkylgroup having 1 to 6 carbon atoms; and each of a and b is an integer offrom 0 to 9, with proviso that a total number of carbon atoms in Formula(III) is from 2 to 18; (C) a monoamine compound represented by Formula(IV):

 wherein each of R¹¹, R¹² and R¹³ is independently hydrogen atom, analkyl group having 1 to 8 carbon atoms, an alkanol group having 1 to 8carbon atoms, an alkanediol group having 1 to 8 carbon atoms, analkanetriol group having 1 to 8 carbon atoms or a group represented by—(R¹⁴O)_(c)R¹⁵; R¹⁴ is an alkylene group having 1 to 4 carbon atoms; R¹⁵is hydrogen atom, an alkyl group having 1 to 18 carbon atoms or an acylgroup having 1 to 18 carbon atoms; and c is an integer of from 1 to 20,with proviso that: (i) at least one of R¹¹, R¹² and R¹³ is an alkanediolgroup having 1 to 8 carbon atoms, an alkanetriol group having 1 to 8carbon atoms or a group represented by —(R¹⁴O)_(c)R³⁵, wherein R³⁵ is analkyl group having 1 to 18 carbon atoms or an acyl group having 1 to 18carbon atoms; or (ii) in a case where at least one of R¹¹, R¹² and R¹³is an alkanol group having 1 to 8 carbon atoms or a group represented by—(R¹⁴O)_(c)H, at least one of the other groups is an alkyl group having1 to 8 carbon atoms; (D) a polyamine having three or more amino groupsin its molecule; (E) an ether group-containing amine; and (F) aheterocyclic compound having nitrogen atom.
 2. A polishing compositioncomprising the improver of claim
 1. 3. The polishing compositionaccording to claim 2, further comprising an abrasive, a pH adjustingagent, or a mixture thereof.
 4. The polishing composition according toclaim 2 or 3, which is used for removing an insulating film which hasbeen embedded for isolation into a trench formed on a silicon substrateand sedimented outside the trench, thereby planing a surface of thesilicon substrate.
 5. A process for selectively increasing a ratio of apolishing rate of an insulating film to that of a stopper film,comprising applying the improver of claim
 1. 6. A process for producinga substrate to be polished, comprising applying the polishingcomposition of claim
 2. 7. A process for producing a substrate to bepolished, comprising applying the polishing composition of claim
 3. 8. Aprocess for producing a substrate to be polished, comprising applyingthe polishing composition of claim
 4. 9. A polishing process comprisingremoving an insulating film which has been embedded for isolation into atrench formed on a silicon substrate and sedimented outside the trenchwith the polishing composition of claim 2, thereby planing a surface ofthe silicon substrate.